In a front gear for a bicycle, a device for buffering an impact by a pedalling force (driving force) caused when a driver starts pedalling has hitherto been well-known as disclosed in Japanese Utility Model Publication Gazette No. Sho 6-10805.
Such conventional device is constructed such that a support member having a plurality of radially extending arms is mounted on a crank comprising a crank shaft and a pair of crank arms. A gear body is provided at its outer periphery with a large number of teeth and is supported rotatably relative to the crank. Between the support member and the gear body is provided a driving force transmitting elastic member, with the driving force of the crank being transmitting to the gear body through the elastic member, thereby buffering an impact caused by the driving force when pedalling starts.
Such conventional device, however, is provided at a driving force transmission for transmitting the driving force of the crank with an elastic member through which the driving force is transmitted to the gear body. In other words, the driving force is not directly transmitted to the gear body and always acts on the elastic member, thereby creating a problem in that the elastic member becomes fatigued easily.